A pressure vessel or pressure tank is normally utilized in industrial and residential pressurized water systems as an accumulator tank for the storage of water. However, pressure vessels are also used to store and transmit other liquids, vapors, and gases under pressure. The pressure vessel is generally connected in line with a supply source that includes a pumping device. The pressure vessel can supply water under pressure for low demand periods without requiring the pumping device to turn on. For higher demand periods, the pressure vessel may allow the pump to run for recommended minimum periods while not interrupting the demand requirements. In order for the pressure vessel to act in this manner, air under pressure contained in the vessel is compressed as water is pumped into the vessel. As more water enters the vessel, a pressure rise results, and the pump will shut off at a predetermined sensed pressure. The cycle will not repeat until a demand relieves the vessel pressure to a predetermined low sensed pressure, which will turn on the pump to refill the pressure vessel.
Typically, the pressure vessel includes two complementary cup-shaped sections that are made of metal, which requires assembly with, e.g., welding to, a metal clamp ring that is disposed inside of the two tank sections. The pressure vessel may further include a valve stem typically disposed in an upper portion of the vessel for measuring air pressure inside of the pressure vessel. The valve stem is often covered by a cap to inhibit interference or damage to the valve stem. A typical pressure vessel is relatively expensive and labor and time intensive to manufacture. Moreover, metal pressure vessels can corrode from external environmental exposure, which can lead to deterioration of the pressure vessel and the water system. Such deterioration can lead to undesirable results, such as leaking vessels.
Conventional pressure vessels also include a separator bag or deformable diaphragm that divides the vessel into two sections. The diaphragm separates gas in one section of the vessel from water in the other section of the vessel and the rest of the system. The gas section is pre-charged with gas under pressure so that the diaphragm is displaced to increase or decrease the volume of the gas section according to the variations of the volume of water in the other section. An air valve extends through one end of the vessel, and an inlet and outlet aperture is provided at the other end of the vessel for fluid communication with the water system. As water is pumped into the vessel, the bag or diaphragm is forced upwardly by the incoming water.
Additionally, the separator bags or diaphragms are usually attached to the pressure vessels in one of two ways. First, the separator bags are either peripherally sealed, or otherwise attached to the sidewall of the pressure vessel, usually at an assembly seam. Second, the pressure vessel may include a removable cell (including the separator bag) that may be removed and replaced upon failure. Both arrangements have advantages and disadvantages. The primary advantage of a diaphragm-type separator attached to, or peripherally sealed to, the sidewall is that the diaphragm may be constructed from a relatively heavy gauge plastic or rubber material, and may be shaped to conform to the cross-section of the vessel or in a manner to eliminate stretching. This arrangement, however, involves the problem of providing a pressure-tight seal between the mating halves of the pressure vessel and between the sidewall of the vessel and the diaphragm. For the sake of economy, attempts have been made to combine the seal between the vessel halves and the seal between the diaphragm and the sidewall into a single assembly. This arrangement, however, has not been entirely successful and may result in vessel leakage. Furthermore, these attachment arrangements usually involve protruding flanges and clamps on the exterior of the vessel that interfere with attempts to helically wind the vessel for added reinforcement (e.g., using a filament winding process).
One known system discloses a split tank closure and diaphragm assembly for a hydropneumatic filament wound pressure vessel. The assembly includes first and second cup shaped plastic tank liners having oblate ellipsoidal end portions and cylindrical sidewall portions terminating in cylindrical open mouth portions. A ring is provided for joining and sealing the open mouth portions together to form a sealed container and to mount a diaphragm within the tank to divide the interior of the tank into variable volume chambers. However, the mounting ring and diaphragm are separate elements that may not provide a pressure-tight seal between the first and second cup shaped plastic tank liners of the pressure vessel and between the sidewall of the vessel and the diaphragm.
Another known system discloses a water pressure tank for use with pumping systems. The water pressure tank includes a pair of tank sections having matching open ends, surrounded by assembly flanges. The assembly flanges are provided with matching bolt holes so that the pair of tank sections can be united by bolts. A peripheral rim of a diaphragm having concentric circular corrugations is clamped between the assembly flanges. Thus, the diaphragm is permitted to expand in either direction from an intermediate position within the pressure tank. However, the assembly flanges protrude outwardly beyond an outer surface of the pressure tank and may interfere with attempts to helically wind the tank for added reinforcement (using a filament winding process).
In addition, if loss of pneumatic pressure is encountered, the diaphragm is typically not restricted from movement within the pressure tank causing the pressure tank to become completely filled with water. This undesirable condition may be the result of a faulty o-ring, a valve stem malfunction, or a worn valve stem cap, for example. Attempts have been made to combine a diaphragm restrictor and the seal between the diaphragm and the sidewall in a single assembly. This arrangement, however, has not been entirely successful and tank malfunction and leakage has resulted.
Further, conventional valve stem and valve cap assemblies do not extend, or extend a small amount, beyond the top of the pressure vessel, making it difficult to access the valve stem to check the vessel pressure. Additionally, conventional pressure vessels often include a valve cap that covers the valve stem and a separate pole piece cap that covers the valve stem and valve cap assembly. The various cap assemblies may be relatively expensive and time intensive to manufacture. Moreover, conventional valve stems tend to develop slow leaks over time due to improper sealing mechanisms in the various cap assemblies, which may lead to incorrectly pressurized vessels.
Therefore, it would be desirable to provide a non-metallic vessel assembly that does not affect the quality or taste of water being held in the vessel and does not deteriorate over time in a corrosive environment. It would also be desirable to provide a non-metallic vessel assembly with an internal diaphragm that is seamlessly installed and interposed between the water chamber and the gas chamber to separate the water from pressurized gas and provides a positive seal between vessel liners. Furthermore, it would be desirable to provide a non-metallic, diaphragm-type vessel assembly that can be mechanically locked together with fiberglass winding tension and can withstand the internal pressures normally associated with vessel assemblies.
It would also be desirable to provide a vessel assembly that provides easy access to the valve stem for checking vessel pressure while at the same time protects the air stem from damage during transit and normal use. It would also be desirable to provide a vessel assembly that seals the air stem from the valve stem to inhibit air leaks, as well as protect the air stem from debris. Furthermore, it would be desirable to provide a diaphragm-type vessel assembly that combines the support ring and a hydrostatic restrictor into one component that provides compression on the diaphragm joint connection and limits the hydraulic movement of the diaphragm, thereby allowing hydraulic pressure or pneumatic pressure to freely pass through the pressure vessel during normal use.